Resistance unit.



E; N. LIGHTFOOT.

RESISTANCE UNIT.

urmorrxon nun MAY4. 1908.

947,247, Patented Jan. 25, 1910.

2 SHEETS-SHEET 1.

E. N. LIGHTFOOT.

RESISTANCE UNIT. APPLICATION FILED MAY4. 1908.

947,247. Patented Jan.,25,1910.

2 SHEETS-SHEET 2 55 parts of the UNITED sra'rps PATENT oFFioE.

EDWIN N. LIGHTFOOT, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR .TO THE CUT- LEE-HAMMER MFG. ('30., OF MILWAUKEE, WISCONSIH,

CONSIN.

Application filed May 4,

n drawing, forming a part of this specification.

-My invention relates to electrical resistances.

.More particularly it relates-to resistance units of the type used in telephone systems,

' but it should be understood that my 1nven-= tion is not limited to resistances used in such service.

Oneobject of my invention is to provide a resistance unit constructed entirely of noncombustible material.

f A further object is to provide a unit of such construction that a maximum number of the same may be mounted in a given space.

A further object is to provide a unit of a given sizewith' the largest possible winding space to secure the maximum amount of re 'sistance.

A further object is to provide means for dividing the resistance of each unit into 'steps.

According to the preferred form of my invention the resistance comprises a wire LWOllIld on a base of noncombustible insulatingmaterial carrying suitable terminals to which the resistance is electrically connected,

the entire unit with the exception of the terminals being inclosed in a non-conducting fire-proof casing.

In order that my invention may be more clearly understood, I have illustrated, in the accompanying. drawings, one embodiment thereof.

V In the accompanying drawings-Figure 1 is' a plan view of a. res stance unit constructed in accordance with my invention. Fig. 2 is a view similar to Fig. 1, but showing the resistance unit with the casing removed.

Fig. 3 is a side elevation of Fig. 2. Fig. 4: is-

a section taken on line M Fig. 1. Fig. 5 isa section taken on line 5-5 Fig. 2. Fig. 6-is a sectional View taken on line 6-6 Fig. "1. Figs Specific'ation of Letters Patent.

residing at 7, 8, 9-'and 10 are'detailed views of A CORPORATION OF WIS- RESISTANCE UNIT.

Patented Jan. 25, 1910. 1908. Seria1No.430,841.

. tailed view of a portion of Fig. 3 showing the resistance coil in sections.

Referring to the construction illustrated in the drawing, the severalparts thereof are mounted upon a base A, best illustrated in Fig. 7 The base comprises a thin rectangular strip of non-combustible and non-conducting .material such as asbestos board, porcelain or soapstone, but in practice I prefer to use the former. 1t shouldbe understood that the size and shape of the base may be varied as desired and that any suitable material may be employed therefor. Two recesses a and a are formed in the base, the former extending the entire length thereof, and the latter about half the length thereof. These recesses are preferably located as illustrated in the drawing, but the-location thereof may be changed as desired. The recess a is provided to receive a conducting strip B and is of greater depth than the width of the strip for the purpose hereinafter set forth. The strip'B has'its ends turned back onto the outside of the base.

Secured to one end of the base, at opposite sides thereof, are terminals 0 and l). The terminal C comprises a bifurcated portion a, and an elongated portion 0, partially screwthreaded, and provided at'its extremity with a flattened portion 0 through which extends an orifice a". The terminal D is similar in construction and comprises a bifurcated portion cl and an elongated portion d, partially screw-threaded and provided at its extrema ity with a flattened portion 6Z through which extends an orifice d. The bifurcated portions of these terminals are adapted to clamp onto the base and are secured thereto by pins or rivets c and d. As will be hereinafter explained, the screw-threaded means by which the units are secured to a supporting panel. The bifurcatedportion 0 of the terminal C is electrically connected to the end 6 of the strip. B, the connection being made in any suitable manner, as by soldering the same together. 0 also passes through the strip B and. serves to retain the 'same against the rear Wall of therecess a and out of contact with turns of thev resistance. The slot a, is provided to receive one end of a terminal or conducting strip E, while the other end of said stri'p projects beyond the base to a point even with the'ends of'the terminals C and D. The

portions of the terminals C and D provide.

ice

The pin or rivet of its terminals.

strip E is preferably of the same thickness as the depth of the slot at, so that its upper face will lie flush with the surface of the base. A thin sheet of insulating material 6, such as mica, is placed over the recess a, but is arranged to leave the extremity e of the strip E exposed. A bifurcated clip G having an opening g therein, through which the strip E projects is clamped onto the base over said strip. A pin or rivet g serves to secure said clip, and the strip E to the base.

The resistance R preferably comprises a fine wire wound around the base A transversely thereof, and in such a manner that only one turn of wire passes over the exposed end 6 of the strip E, and this turn is soldered or otherwise electrically connected thereto. The terminal 1" of the resistance is soldered or otherwise electrically connected to the end Z) of the conducting strip B,

of the resistance is $01-- while the terminal r dered or otherwise electrically connected to the terminal D. It will thus be seen that the terminals G and -D are connected to opposite ends of the resistance coil R, the terminal C being connected thereto through the strip B, while the terminal E affords means for' dividing the resistance into two steps. While I have shown the resistance divided into two steps it should be understood that the terminal E may be dispensed with if de; sired, or the resistance may be divided into a greater number of steps b merely providing additional terminals simi ar to the terminal E and connecting the same to the resistance at different points. Resistances of this type are frequently mounted side by side in rows on the rear side of a supporting panel with their terminals extending through apertures formed in the supporting panel and projecting beyond the front face thereof. The

units are secured to the supporting panel by nuts which are screwed onto the threaded portions of their terminals and bear against the face of the panel. This manner of mounting the units is well known and is, therefore, not illustrated. When the units are mounted as above described, it is desirable to place the same as close together as possible in ordef to reduce the side of the supporting panel. In order that the units may be placed in close proximity itis essential that some means be provided for insulating the same from one another and for preventing the jumping of an are from one to another, in the event one of the units.

burns out, as otherwise an entire row of units might be destroyed upon the burning out of one of the same. To obviate this danger, and to insulate the units from one an-- other I provide each unit with a fireproof insulating casing F which inclose's all of the conducting parts thereof, with the exception This casing may assume any desirable form, but preferably comprises B from the turns of the resistance, but it should be understood that this is not essential, as the strip B is maintained at the rear of the recess out of contact with the resistance by therivet c. The cement may be applied in any practical manner, and ma com rise any suitable ingredients. While I pre er to use cement for the casing, it should be understood that the casing may comprise any suit-able material, and may be made detachable if desired. The casing may also be made Waterproof if desired.

It will thus be seen that resistance units constructed in accordance with my invention occupy a very small space and that the same may be placed in very close proximity without danger, as they are well insulated and any are caused by the burning out of one of the units would be quickly smothered within its casing and rendered harmless.

Havingthus described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a resistance unit, the combination with a fireproof insulating base, of a'resist- .ance carried thereby, a pair of terminals mounted on one end of said base, one of said terminals being electrically connected to one end of said resistance and an insulated conducting strip interposed between said base and said resistance for connecting the other of said terminals to the resistance.

2. In a resistance unit, the combination with a fireproof insulating base, of a resistance wound thereon, a pair of terminals mountedon one end of said base, one of said terminals being electrically connected to one end of said resistance and a conducting strip connecting the other of said terminals with the opposite end of said resistance, said conducting strip being embedded in said base and maintained out of contact with the turns of said resistance.

3.'In' a resistance unit, the combination with a fireproof insulating base, of a resistance carried thereby, a pair of terminals mounted on said base and electrically connected to opposite ends of said resistance and another terminahcarried by said base and connected to said resistance intermeopposite end of said diate of its ends, said last mentioned terminal having an insulated portion interposed between said baseand said resistance.

4. In a resistance unit, the combination with a fireproof insulating base, of a resistance wound thereon, of a plurality of terminals mounted on one end of said base, one of said terminals being electrically connectsaid resistance, a conducting strip fitting in I one of said recesses in said base for connectsaid terminals being connected by an insunals mounted on one end of said base, one

ed to one end of said resistance, another of said terminals being connected to said resistance intermediate of its ends and having a portion thereof embedded in said base and insulated from said resistance, and a conducting strip connecting another of said terminals to the opposite end of said resistance, said conducting strip being embedded in said base and maintainedout of contact with the turns of said resistance. 5. In a resistance unit, the combination with afireproof insulating base having longitudinally extending recesses formed therein, of a resistance wound on said base transvcrsely thereof, a pair of terminals carried at one end of said base, one of said terminals being electrically connected to one end of ing the opposite end of said resistance to the other of said terminals, a third terminal having a portion thereof fitting in another of the said recesses in said base and electrically connected to said resistance intermediate of its ends,and means for maintainin said last mentioned terminal and said conducting strip out of contact with the turns of said resistance. 7

6, In a resistance unit, the combination with a fireproof insulating base, of a resistance carried thereby, terminals carried by said base and electrically connected to said resistance at different points, said terminals being adapted to support said base and a fireproof insulating casing inclosing the resistance bearing portion of said base.

7. In a resistance unit, the combination with a fireproof insulating base, of a resistance carried thereby, terminals mounted on one end of said base, one of said termi na-ls beingelectrically connected to one end of said resistance, an insulated conducting strip connecting the opposite end of said re sistance with the other ofusaid terminals, and a fireproof insulating casing substantially inclosing said base, said resistance and said conducting strip.

8. In a resistance unit, the combination with a fireproof insulating base, of a resistance carried thereby, a plurality of terminals mounted on one end of said base, one of said terminals being electrically connected to one end of said resistance, another of lated portionto said resistance intermediate of its ends, an insulated conducting strip connecting another of said terminals to the opposite end of said resistance, and a fireproof insulating casing inclosing said base and all of the conducting parts except said terminals.

9. In a resistance unit, the combination with afireproof insulating base, 'of a resistance wound transversely thereon, termi-,

- connecting the cut of said terminals being electrically connected to one end. of said resistance, a conducting strip embedded in said base out of contact with the turns of said resistance for connectingthe opposite end of said resistance with the other of said terminals and a fireproof insulating casing inclosing said base and all of the conducting parts except said terminals.

10. In a resistance unit, the combination with a fireproof insulating base, of a resistance Wound transversely thereon, termi- -nals mounted on one end of said base, one

of said terminals being electricallyconnected to one end of said resistance, a conducting strip embedded in said base out of contact with the turns of said resistance for opposite end of said resistance with the other of said terminals, another terminal connected to said resistance intermediate of the ends and having a portion embedded in said base and insulated from the turns of said resistance, and a fireproof insulating casing inclosing said base and all of the conducting parts except said terminals,

11. In a resistance unit, in combination, a non-combustible insulating base, a resistance mounted thereon, and terminals secured to said base and connected to said resistance at different points, said terminals being adapted to support said base.

12. In a resistance unit, in combination, 7 a non-combustible insulating base, a resistance mounted thereon, terminals secured tosaid base and connected to said resistance at different points, anda cement covering substantially inclosing said base and said're' sistance and adhering to said base.

13. In a resistance unit, in combination, a fiat elongated base formed of non-combustible insulating material, a resistance mounted thereon, terminals secured to one end'of said base and connected to said resistance at different points, said terminals beingadapted 1 10 to support said base, and a cement covering substantially'inclosing said base and said resistance, said cement-covering being adapted to adhere to said base.

14. In a resistance unit, in combination, a non-combustible insulating base, a. resist- .ance wound thereon and elongated termi- 'nals, each having a bifurcated portion adapted to fit=over an edge of said base, and to be rigidly secured thereto, said terminals being'connected to said resistance at differ- OllltS. 15. In a resistance unit, in combin tion, anon-combustible insulating basefaf' resistance wound thereon, terminals secured to said base at one end thereof, andelectrically connected to said resistance at different points, certain of said terminals having extensions disposed between said base and said resistance, and means for maintaining said flBQ extensions out of contact with said resistance, except at the points of connection therewith. v

16. In a resistance unit, in combination, a non-combustible insulatingv base, a resistance wound .thereon, terminals secured to said base at one end thereof and electrically connected to said resistance at diiferentpoints, certain of said terminals having portions interposed between said base and said resistance, means for maintaining said portions of said terminals out of contact with.

said resistance, except at the points of connection therewith and a cement covering adhering to said base and substantially inclosing said base and said resistance.

'17-. Ina resistance unit, in combination,

.a flat-elongated base formed of non-combustible insulating material, a resistance wound thereon, terminals secured to one. end of said base and connected to said resistance at different points, certain of said terminals havingportions disposed in recesses in said base, means for maintaining said portions of said terminals out of contact with said resistance, except at the points of connection therewith and a cement covering adhering to said base and substantially inclosing said base and said resistance.

18. In a resistance unit, in combination, a flat elongated base formed of non-combustible insulating material, a resistance Wound thereon, terminals for said resistance, and a cement covering adhering to said base and substantially inclosing said base and said resistance;

In witness whereof, I have hereunto subscribed my name in the presence of two witnesses.

EDWVIN N. LIGHTFOOT.

Vitnesses FRANK H. HUBBARD, S. ITZ GERALD. 

